This invention relates generally to devices for measuring the trajectory or flight path of a projectile. More specifically, it relates to systems using an array of light beams to determine the position, velocity and trajectory of a sphere or ball, such as a baseball as it passes through the Strike Zone.
Devices for determining the velocity and position of a ball are numerous in the art. These devices are typically used in sports training or sports games including especially baseball and golf. In the game of golf, such devices are often used to determine the flight path of the ball. In the game of baseball, such devices are frequently used to determine ball location or ball speed at the Strike Zone.
The inventions in the art can be grouped into several different categories depending on the technologies used. One method prevalent in the art uses radar systems. Another common method is the use of cameras and associated image processing. Ultrasonic sensors are also used, as are mechanically activated switches.
Another common method in the art, related to the current invention, utilizes light beams or laser beams and light detectors organized in an array. U.S. Pat. No. 4,949,972 uses a light array of crossing light beams to indicate the location of a projectile passing through the array. U.S. Pat. No. 7,944,549 uses an optical screen formed by a single light source and an array of detectors which receive the reflected light from the object in motion. U.S. Pat. No. 7,367,906 uses two light beam arrays. A first array detects horizontal position, a second array located a known distance from the first detects vertical position, and the know distance between arrays is used to calculate the velocity of the ball. U.S. Pat. No. 7,295,329 uses two light sources and light detectors to determine location of a moving object. U.S. Pat. No. 5,333,855 uses a light beam array with alternating emitters and detectors and calculates the length of time it takes for the ball to travel through the array as the basis for ball velocity. Ball position is determined by the location of obscured detectors. U.S. Pat. No. 6,985,206 uses two or more light curtains (potentially at the front and back of the strike zone) and measures the time it takes the ball to travel between light curtains to determine the velocity of the ball. U.S. Pat. No. 5,479,008 uses parallel light beams to calculate an instantaneous spatial position of a sphere in order to calculate a horizontal launch angle of a golf ball. This patent calculates the height dimension of the sphere based on information obtained from the light screen. U.S. Pat. No. 5,631,558 measures velocity using 2 parallel planes at a set distance apart; additionally, 2 groups of sensors arranged in an arc. The velocity of the sphere is not determined directly from the light screen but is calculated from the time it takes to traverse from a first group of sensors to a second group of sensors.
The drive for improvements in the art is due largely to the need for precision and accuracy at low cost. Cost is an important consideration since it is possible to obtain an accurate trajectory of a projectile using carefully located high speed cameras and associated image processing. However, this approach is prohibitively expensive for many applications.
The inventions, related to the current technology, available in the art, measure components of position (x, y and z components) and/or components of velocity (velocity in the x, y and z directions). In many circumstances, it is the velocity components perpendicular to the principle axis of flight (the x and y directions) that are most important. For example, the effectiveness of a breaking ball in baseball is largely based on the velocity of the ball in the directions perpendicular to the principle line of flight. It is here that the current inventions in the art fall short. None of the methods in the art accurately calculate the velocity without assuming a straight flight path (i.e. x and y components are assumed to be zero). This limits the usefulness of the information. For example, since the effectiveness of a baseball pitch (such as a breaking ball) is almost entirely based on the non-linear characteristics of the flight path, the assumption of a linear trajectory results in information that is of little value for analyzing curve ball effectiveness. The current invention provides nonlinear position, trajectory and velocity information with accuracy which is not available in the current state of the art for a simple, low cost apparatus.
Therefore, it is a primary objective of the current invention to provide more complete information on position and velocity than is currently provided; an improved measuring apparatus that precisely defines both the spatial position of the ball at the Strike Zone and additionally, the velocity vector (velocity and trajectory) of the ball at the Strike Zone while at the same time eliminating the assumption of a straight line trajectory.
It is a further objective of the present invention to provide a method for determining position and velocity that is more accurate than current methods. An accurate calculation of trajectory is required to make an accurate determination of Strike or Ball. Accuracy is also important to coaches and trainers as well as applications beyond sports.
It is still a further objective of the present invention to provide a method of determining position and velocity that is simple and low cost.